1. Field of the Invention
This invention relates to a steering system which uses a unique compensating valve and more particularly, to a hydrostatic power steering control system with variable volume feedback compensation.
2. Description of the Prior Art
The use of hydraulic steering cylinders to control the position of the steerable wheels on a vehicle, especially off-road type vehicles, is commonplace. Normally, a mechanical linkage is employed which connects the two steering arms together in such a manner as to cause the outside wheel to generate a greater turning radius than the inside wheel. Since it is also common practice to connect the steering cylinders to extensions of the steering arms, the cylinders experience differences in piston velocities during a steering cycle. These variations in piston velocities cause fluctuations of the fluid flow rates that are detrimental to the control of the vehicle if they are not corrected.
Several solutions to correct for the differences in piston velocities have been proposed. One such solution is the use of an equal area displacement cylinder as taught by L. Blatt et al in U.S. Pat. No. 3,949,650 issued Apr. 13, 1976, in the steering system. Another solution proposed by applicant is the use of two interconnected equal area displacement cylinders with constant volume feedback. Both of these systems are satisfactory but do not allow for a steering control system wherein hydraulic cylinders having only two internal chambers are used. The use of cylinders having two such chambers reduces the need for closer piston rod tolerances, lessen manufacturing time and lower the cost of the cylinders. Now a steering control system with variable volume feedback compensation has been invented which uses hydraulic cylinders having only two internal chambers.